For people who suck at poker. When you lose all of your all-important 'internet money' on a poker site, you can refill your online 'bank account' to get you going again. You usually get 2 refills a day. Once they are gone, you'll need a new poker account to get more play money. Refills are the last grasp of a poker 'no-one' becoming a poker 'someone'. Sadly, this does not apply in real life.

'Garry, I just went all in with four kings!'
'Did ya win!?'
'Nope...lost to some jew wearing a cowboy hat'
'Time for a refill....'